Plasma Bombardment-Induced Amorphization of (TiNbZrCr)N_x High-Entropy Alloy Nitride Films

Round 1

Reviewer 1 Report

Review on the Manuscript entitled:

 Plasma Bombardment Induced Amorphization of (TiNbZrCr)Nx High-Entropy Alloy Nitride Films

 Dear Editor,

The authors have investigated (TiNbZrCr)Nx high-entropy nitride films (HENFs) were prepared by high-power pulsed magnetron spuering (HPPMS). The effect of N2 flow rate (FN) on the HPPMS plasma discharge, film composition, microstructure, residual stress, tribological properties and corrosion resistance were investigated. In my opinion, the subject of this manuscript is very interesting and applicable in industry. I recommend this article for publishing in the Coatings; however, it needs some major revisions:

1. “Firstly, the introduced N atoms react with Ti, Nb, Cr and Zr to form an FCC nitride phase structure”. Would you please describe the reason for selecting the metals of Ti, Nb, Cr and Zr. Ti and Cr are in the first row transition metals while  Nb and Zr belong to the second row and Nb is  under vanadium. Have you encountered with the similar work in the literature?

2.  Page 2, lines 63–67 “Many reports have shown that the N atoms will react with elements such as Ti, Ta, Hf, Al, Ti, Zr, Mo, V, Nb, Cr to form an FCC structure with multiple elements, while films without N are mostly amorphous. The incompatibility between amorphous SiN and the FCC (AlCrTiZrMo)N phase caused SiN precipitate at the interface, resulting in a composite structure of amorphous SiN and nanocrystalline (AlCrTiZrMo)N”. There is no citation.

3. Have you applied the alloy of Ti, Nb, Cr and Zr? Describe it.

4. Page 2, lines 80, 81: “…they are all nitride forming elements that easily combine with N to form a single-phase FCC structure” Do the authors want to refer the charge transfer between nitrogen and transition metals. Have you studied the amount of charge transfer between these atoms as electron donner and electron acceptor?

5. Experiments section was prepared well. However, it is recommended to replace the name of Experiments section to the Materials and Experimental methods.

6. Results and Discussion in the subsection of 3.1 & 3.2 …was stated with Figure1 & Figure 2. I think it is better the authors represent some lines for describing and then remark the Figure 1 & Figure 2….

7. Figure 5 , part (c) “Young’s modulus of (TiNbZrCr)Nx HENFs deposited at different nitrogen flow rates” was not represented. Please correct it. Furthermore, define the blue and red dash line in the Figure 5.

8. Please order the description of Fig. 6a, Fig. 6b, Fig. 6c and Fig. 6d. in the text as the presented in the Figure 6. It is confusing for the readers.

9. Figure 8 “…(b-c) Bode plots from EIS data of 316 SS and (TiNZrCr)Nx HENFs….” It is recommending separated part b and c.

10. Page 11, line 314: “Table 3 displays the electrochemical impedance…”. It is needed to introduce all parameters of Table 3 in the text.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is devoted to the study of the structure and properties of (TiNbZrCr)Nx high-entropy nitride films. Films were prepared by high-power pulsed magnetron sputtering (HPPMS). The authors studied the dependence of the film structure on the production conditions. They found that the corrosion resistance of the (TiNbZrCr)Nx films shows a strong correlation with the amorphous phase: corrosion resistance gradually increases with the amorphous transformation of the film. The best tribological property was observed in the HENFs deposited at FN = 12 sccm.

Remarks:

1.      In Figure 2, the peak from the amorphous phase is almost invisible.

2.      Line 170. The authors write that “…the (200) plane has the lowest surface energy.” It is not clear why the (200 ) plane in the FCC lattice has the minimum surface energy. Typically, in an fcc lattice, the planes of maximum close packing have the minimum surface energy, i.e. plane (111).

3.      Line 177. It is not clear how the size of the crystals was estimated using Scherer’s formula, or how the background was subtracted. Section 2 does not say anything at what height of the peak its width was measured. A method for determining the size of nanocrystals from X-ray diffraction patterns should be added to Section 2.

4.       Line 222. The electron diffraction pattern (Figure 4c) should show a halo from the amorphous matrix and ring reflections (111) and (200) from the nanocrystals. Electron diffraction pattern must match X-ray diffraction pattern and HREM image (Fig.4b). Meanwhile, in (Figure 4c) only a halo from the amorphous matrix is visible; reflections from nanocrystals are not visible at all. If the authors believe that only (200) reflections are visible, then where are the (111) reflections? Where is the halo from the amorphous phase? The structural data need to be discussed in more detail. They should not contradict each other. If the proportion of the amorphous phase is significant, then reflections from nanocrystals may be weak and not appear in the electron diffraction pattern. As a rule, in X-ray diffraction patterns and electron diffraction patterns from amorphous-crystalline samples of metal systems, the position of the first line from the crystalline phase (in this case, the line (111), not (200)! is close to the position of the diffuse maximum from the amorphous phase. Therefore, the authors need to explain why they do not observe (111) reflections and scattering patterns from the amorphous phase in the electron diffraction pattern. Why did they conclude that the reflections observed in Figure 4c correspond to reflections (200).

5.      Section 2 does not provide information about the type of electrons used to obtain images (Figure 3a,c,d,e).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

I have thoroughly reviewed the article titled "Plasma Bombardment Induced Amorphization of (TiNbZrCr)Nx High-Entropy Alloy Nitride Films."  Authors are encouraged to carefully consider the provided remarks to enhance the clarity, rigor, and impact of their work.

1) In the XRD diffraction pattern we see the Si peaks. This is an interesting observation, especially considering that the authors expect nitrides such as TiN, CrN, NbN, ZrN and HfN

2) From how many diffraction peaks and from which diffraction peaks was the grain size calculated using the Scherrer equation? Was it calculated from the peaks with the same 2-theta angle peak?

3) Line 208 " The observed grain size in TEM is different from the XRD calcula tion results, which may be due to the fact that the prepared TEM sample is a planar sample and the grain size in the growth direction of the thin film cannot be observed" It is obvious that the XRD allows the calculation of the crystallite size and not the grain size. From this reason this comparison does not have any sense.

4) Line 248 - "The increase in hardness is attributed to the formation of nanosized nitride phases" Do the authors have any evidence to support this statement?

5) The caption of Figure 8 contains the information "Figure 8. (a) Nyquist, (b-c) Bode plots”, while the text contains the opposite information “The Bode plots (Fig. 8a) and Nyquist plots (Fig. 8b and 8c)”

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Review Letter

Dear Editor,

Regarding the author’s revision, I am pleased to inform my satisfaction of present form of the manuscript entitled: “Plasma bombardment induced amorphization of (TiNbZrCr)Nx high-entropy alloy nitride films” for publication in Coatings.

Reviewer 2 Report

The authors have improved the text. The article may be published in its present form

Reviewer 3 Report

Manuscript can be accepted in present form.